Tides

Section 13.2

What are tides?

• The daily rise and fall of Earth’s waters on its coastline

• High Tide – when water reaches its highest point on shore

• Low Tide – When water reaches its lowest point on shore

What are tides?

Tides occur in all bodies of water but are most noticeable in large lakes and oceans

Tides occur on Lake Superior, too

What causes tides?

• Tides are caused by gravity between the Earth, moon, and sun

What causes tides?• The moon’s gravity pulls on Earth’s

surface closest to the moon causing water to create a bulge

• Water is stolen from the sides to create the bulge

• The side of Earth furthest from the moon has the least effect of moon’s gravity and is acted on by centrifugal force

• video

Different kinds of tides

• Most coastlines experience 2 high tides that are about 12 hours 25 minutes apart

Different kinds of tides

• The sun’s gravity can add to the moon’s pull or even it out depending on the positions of the sun, moon and Earth

Different kinds of tides

• Spring Tides- highest high tides, lowest low tides- sun, moon, & Earth are in line

• Neap Tides- lowest high tides, highest low tides- sun, moon, & Earth are at right

angles

Spring Tide

Neap Tide

High and low tides are affected by:

• Landforms that interrupt water movement

• Basins at the mouth of a river

• The depth of moving water in a narrow channel

Using Tides

• Potential energy from tide heights can be harnessed to create electricity

Tidal Plants HydroelectricDam

Bay of Fundy

The tidal difference is 25 feet